Relative pose estimation has been studied for centuries, first in the photographic and later in the computer vision community. Nevertheless, due to the fundamental relevance to many state-of-the-art applications in structure from motion and simultaneous localization and mapping, research is ever evolving in recent years. The core challenge of relative pose is to estimate the motion between two camera poses, revealing 3D reconstructions of the environment as well as camera odometry.
Classic approaches study the location of point correspondences in multiple views and their relationship to pose recovery. In the case of unknown intrinsic calibration, an 8 point algorithm or 7 point algorithm is most frequently employed to recover the fundamental matrix and a 6 point algorithm is used for unknown focal length. With calibrated cameras a 5 point algorithm is most suitable.